| /* |
| * Copyright (C) 2011 The Guava Authors |
| * |
| * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except |
| * in compliance with the License. You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software distributed under the License |
| * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express |
| * or implied. See the License for the specific language governing permissions and limitations under |
| * the License. |
| */ |
| |
| package com.google.common.base; |
| |
| import static com.google.common.base.Preconditions.checkNotNull; |
| |
| import com.google.common.annotations.GwtCompatible; |
| import com.google.common.annotations.GwtIncompatible; |
| import java.io.Serializable; |
| import java.lang.ref.WeakReference; |
| import java.lang.reflect.Field; |
| import java.util.EnumSet; |
| import java.util.HashMap; |
| import java.util.Map; |
| import java.util.WeakHashMap; |
| import org.checkerframework.checker.nullness.compatqual.NullableDecl; |
| |
| /** |
| * Utility methods for working with {@link Enum} instances. |
| * |
| * @author Steve McKay |
| * @since 9.0 |
| */ |
| @GwtCompatible(emulated = true) |
| public final class Enums { |
| |
| private Enums() {} |
| |
| /** |
| * Returns the {@link Field} in which {@code enumValue} is defined. For example, to get the {@code |
| * Description} annotation on the {@code GOLF} constant of enum {@code Sport}, use {@code |
| * Enums.getField(Sport.GOLF).getAnnotation(Description.class)}. |
| * |
| * @since 12.0 |
| */ |
| @GwtIncompatible // reflection |
| public static Field getField(Enum<?> enumValue) { |
| Class<?> clazz = enumValue.getDeclaringClass(); |
| try { |
| return clazz.getDeclaredField(enumValue.name()); |
| } catch (NoSuchFieldException impossible) { |
| throw new AssertionError(impossible); |
| } |
| } |
| |
| /** |
| * Returns an optional enum constant for the given type, using {@link Enum#valueOf}. If the |
| * constant does not exist, {@link Optional#absent} is returned. A common use case is for parsing |
| * user input or falling back to a default enum constant. For example, {@code |
| * Enums.getIfPresent(Country.class, countryInput).or(Country.DEFAULT);} |
| * |
| * @since 12.0 |
| */ |
| public static <T extends Enum<T>> Optional<T> getIfPresent(Class<T> enumClass, String value) { |
| checkNotNull(enumClass); |
| checkNotNull(value); |
| return Platform.getEnumIfPresent(enumClass, value); |
| } |
| |
| @GwtIncompatible // java.lang.ref.WeakReference |
| private static final Map<Class<? extends Enum<?>>, Map<String, WeakReference<? extends Enum<?>>>> |
| enumConstantCache = new WeakHashMap<>(); |
| |
| @GwtIncompatible // java.lang.ref.WeakReference |
| private static <T extends Enum<T>> Map<String, WeakReference<? extends Enum<?>>> populateCache( |
| Class<T> enumClass) { |
| Map<String, WeakReference<? extends Enum<?>>> result = new HashMap<>(); |
| for (T enumInstance : EnumSet.allOf(enumClass)) { |
| result.put(enumInstance.name(), new WeakReference<Enum<?>>(enumInstance)); |
| } |
| enumConstantCache.put(enumClass, result); |
| return result; |
| } |
| |
| @GwtIncompatible // java.lang.ref.WeakReference |
| static <T extends Enum<T>> Map<String, WeakReference<? extends Enum<?>>> getEnumConstants( |
| Class<T> enumClass) { |
| synchronized (enumConstantCache) { |
| Map<String, WeakReference<? extends Enum<?>>> constants = enumConstantCache.get(enumClass); |
| if (constants == null) { |
| constants = populateCache(enumClass); |
| } |
| return constants; |
| } |
| } |
| |
| /** |
| * Returns a converter that converts between strings and {@code enum} values of type {@code |
| * enumClass} using {@link Enum#valueOf(Class, String)} and {@link Enum#name()}. The converter |
| * will throw an {@code IllegalArgumentException} if the argument is not the name of any enum |
| * constant in the specified enum. |
| * |
| * @since 16.0 |
| */ |
| public static <T extends Enum<T>> Converter<String, T> stringConverter(final Class<T> enumClass) { |
| return new StringConverter<T>(enumClass); |
| } |
| |
| private static final class StringConverter<T extends Enum<T>> extends Converter<String, T> |
| implements Serializable { |
| |
| private final Class<T> enumClass; |
| |
| StringConverter(Class<T> enumClass) { |
| this.enumClass = checkNotNull(enumClass); |
| } |
| |
| @Override |
| protected T doForward(String value) { |
| return Enum.valueOf(enumClass, value); |
| } |
| |
| @Override |
| protected String doBackward(T enumValue) { |
| return enumValue.name(); |
| } |
| |
| @Override |
| public boolean equals(@NullableDecl Object object) { |
| if (object instanceof StringConverter) { |
| StringConverter<?> that = (StringConverter<?>) object; |
| return this.enumClass.equals(that.enumClass); |
| } |
| return false; |
| } |
| |
| @Override |
| public int hashCode() { |
| return enumClass.hashCode(); |
| } |
| |
| @Override |
| public String toString() { |
| return "Enums.stringConverter(" + enumClass.getName() + ".class)"; |
| } |
| |
| private static final long serialVersionUID = 0L; |
| } |
| } |